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Despite the particular importance of the subject of soil-structure interaction, unfortunately, this issue has received little attention from engineers, and seismic codes have not given much recommendation to consider its effects. Seismic wave frequencies vary continuously, and the stiffness of springs and damping of dampers connected to structural supports also vary with the loading frequency. To simplify time-domain numerical analysis, a constant target frequency can be used to keep stiffness and damping values constant. In the substructure method proposed in this study, the optimal target frequency is the one that yields results that most closely match those of a more accurate nonlinear 3D model analyzed using a direct method. A common simplification is to ignore the foundation’s non-linear response, justified by design requirements to prevent permanent deformation and the complexity of frequency-dependent soil behavior. Though not fully precise, this approach (considering soil heterogeneity and optimal target frequency) offers a forward-looking analysis and a basis for future nonlinear studies. This study presents a three-dimensional (3D) numerical model for analyzing the seismic response of soil-foundation-structure systems embedded in granular soil (with different relative densities) considering the effects of soil heterogeneity (With varying shear modulus with depth and compatible with the practical HSsmall model). The model is capable of accounting for the effects of loading frequency along with the radiation damping of the soil system and can integrate with the widely-used substructuring method considering an optimal target frequency. After verifying the proposed model, the dynamic equilibrium equations of the substructuring system were solved in the time domain using Matlab software. The target frequency was determined using i) Case 1: the fundamental frequency of the soil (or the dominant frequency of the excitations), ii) Case 2: the fundamental frequency of the structural system, iii) Case 3: the fundamental frequency of the soil-foundation-structure system; iv) Case 4: the fundamental frequency of structure with static stiffness and damping support (Case 4); and v) the fundamental frequency of fixed base structure and modified stiffness, and the results were compared together. A comparison of the impedance (dynamic stiffness and damping) of foundations situated on homogeneous and heterogeneous soil, as well as an investigation of the structural response in both cases, is another objective of this research. The analysis results demonstrated the accuracy of the proposed model and the acceptable calculation speed for estimating the dynamic response of structures located on heterogeneous soils under frequent operational earthquakes. The results also showed that with an increase in soil relative density, the seismic behavior of structures on homogeneous and heterogeneous granular soils converges. For instance, the response of the foundation on homogeneous soil bed with relative densities of 55%, 75%, and 95% is on average 23%, 19%, and 15% lower than that of heterogeneous soil, respectively. Additionally, for determining the target frequency, the use of frequency‐independent Kelvin–Voigt models (i.e., Cases 1-5) provides acceptable responses. According to the data presented in Table 4 and Figs. 9 and 10, the following conclusions can be drawn: 1) The soil's fundamental frequency (Case 1) yielded the least precise results. 2) While Case 3 offered the most favorable response, closely matching the direct method, determining the soil-structure system's fundamental frequency through complex integration in numerical software is often impractical. 3) Employing the target frequency in Case 2 produced more satisfactory results than Case 1. 4) Cases 4 and 5 generated nearly identical frequencies. Compared to Case 2, these cases enhanced response accuracy, bringing them closer to the best response (i.e., Case 3). Therefore, for practical applications, it is recommended to utilize the fundamental frequency from either Case 4 or Case 5 instead of the soil-structure system's fundamental frequency (Case 3) to establish the optimal target frequency.
 

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Abstract In this study, the dynamic behaviour and pore water pressure generation in a typical earth dam were investigated using the non-linear dynamic analyses results. Based on the Byrne version of the Finn’s Model, variations of pore water pressure ratio against the strength parameters of materials and also the dilatancy angle of shell material were considered. In addition, using the scaling method of applying maximum acceleration, the variations of pore water pressure ratio and liquefaction phenomenon were investigated in different maximum accelerations. The results demonstrated that excess pore pressure depends strongly on the strength parameters, dilatancy angle of materials and applied maximum acceleration. Inappropriate compaction of shell material results in severe increase in liquefaction-induced failure potential. In earth dams with appropriate compaction of materials, liquefaction probability in the dam body, is negligible even in large earthquake accelerations.

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Abstract Studying the response details of steel moment connections is very important due to the role of connections in moment resisting frames. The aims of this research were: i) to study the damage indices of steel material including: Pressure Index, Mises Index, Equivalent Plastic Strain Index, Triaxiality Index, and Rupture Index and ii) to compare these indices at connections of steel moment frames under earthquake loads. To achieve this, time history nonlinear dynamic analysis is performed using selected earthquake records on 2D model of special steel frame with ten storey and one bay to determine maximum rotations of connections. Then, damages indices of the selected connections under maximum rotation of records are investigated with selecting two types of moment connections. The results indicate that damage indices are dependent on type of connection, location of surveying, and rotations caused by earthquake movements. This dependency is very considerable for Equivalent Plastic Strain Index and Ruptureindices

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Abstract: The experimental study of structural vibration is often performed to determine the modal parameters of a structure or to verify the theoretical models and predictions. The first phase of this research involved the experimental determination of the modal properties of a rectangular steel tank with different levels of water. The natural frequencies obtained from the experiments were compared to those calculated by the analytical models. In the second phase, a procedure for computing hydrodynamic pressures in rectangular tanks is proposed. This procedure considers the effect of tank wall flexibility in determining the hydrodynamic pressures produced by the impulsive response. Based on a two-dimensional model of the tank wall, a dynamic time-history analysis was carried out. The results were compared with other models based on the current design practice codes and standards, which use a lumped mass approach. The comparison shows that, in most cases, the lumped mass approach overestimates the base shear. The effect of wall flexibility on wall displacements and base shears are also discussed.

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Abstract: Implementation of 3D panels in buildings is increasing due to the importance of lightening, optimizing and reduction of fuel consumption. These panels are used as interior, outer, load bearing and partitioning walls beside the structural frame without considering the frame-panel interaction. Steel frames act in shear mode and panel frames act in flexure; hence, combining the two systems will change the structural behavior of each system. So, investigation of the seismic behavior of combined systems using nonlinear dynamic methods seems to be mandatory. In this article, frames with 3, 5 and 10 stories (filled in different bays by panel) were modeled in ANSYS. These frames were then analyzed under Elcentro, Tabas and Naghan seismic records. The results illustrated that using panel not only results in more acceptable drifts, but also it lets the system to have a better seismic behavior and more energy dissipation. For example, the displacements of the structures in the highest level decrease more than 35% by using one bay panel for filling steel frames. This amount of filling also leads to more than 100% increase in the area under the base shear-displacement diagram of a steel frame.

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Abstract: Because of the complicated nature of track and train, investigation of interactions between them has been always an complex problem in railway engineering. Perceiving of this interaction is an complex problem only in track with various defects but also in the track without defects. Estimating of the forces exerted on track and train will be much difficult when a defect such as rail corrugation is added to this interaction. If an accurate computer model is available, we can have a good forecast of these forces. However, precise estimating of them is only reached field measurement. In this study, we tried to present a good estimation of passenger and freight wagon forces on track with rail corrugation defect. The pressure between sleeper and ballast was calculated by these forces. Afterwards pressure (on ballast surface)-rail corrugation wavelength diagrams was determined. By using these diagrams, the rail corrugation wavelength where ballast stresses were beyond the permissible limit for each type of operation, was determined (it was named critical corrugation wavelength). A computer model was developed in ADAMS/Rail software for passenger and freight wagons with various speeds to estimate the forces exerted on the ballasted track with corrugation defect.

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Progressive collapse of buildings has raised questions on adequacy of the existing regulations to prevent local and, in turn, global collapses. The present study mostly focuses on the performance of welded moment connections against progressive collapse. The performance of moment connections suggested in the FEMA 350, which are proper for seismic forces, Welded Flange Plate (WFP), Reduced Beam Seaction (RBS), Welded Unreinforced Flange- Welded Web (WUF-W) and Free Flange (FF), has been studied. The models used include non-linear behavior of materials and geometrical nonlinear behavior. The behavior of steel materials used in the structure is the true behavior of steel was stress-strain, which has been considered in the model completely. The nonlinear stress-strain behavior of steel selected for modeling the real behavior of beam and column members in the structure. The material properties of all steel components were modeled using elastic-plastic material model from ABAQUS. For connection region porous material plasticity was used. The diagram of vertical force against vertical displacement for each connection was drawn, and the state of each connection failure was investigated. Making the large scale experimental models to study the progressive collapse of structures seems too difficult. Using finite element models to study the behavior of structures are relatively appropriate option with regard to time and cost. In all of the numerical models, shell (S4) element has been used to simulate the beams, columns and connections. This is a four-node element, which contains four integration points on the element. During the calculations, full integration method with more precision was used. For analysis of the models, dynamic explicit method was used. This method is suitable to analyze the models with more members having nonlinear characteristics of materials and large deformations. In this method, the central difference integrating is used to solve the dynamic equations. In every time step, this method performs simpler than other methods in solving dynamic equations since there is no need to inverse stiffness matrix in any time stage. The used numerical method has compared using the laboratorial results, which have tested in 2010 by NIST. The analytical results showed a good agreement with laboratory models. The results of numerical analyses illustrated that RBS connection has less strength in comparison with other connections and this connection reaches maximum vertical displacement with less force. Performance of FF and WUF-W connections is similar to each other. These connections more resistant in comparison with RBS. WFP connection is more resistant as compared with the WUF-W, FF and RBS connections against the failure of the column. Failure load in WFPconnection is twice of other connection, and according to the analytical results, this connection is suitable for HLOP structures. In all connections, rotation capacity corresponding to collapse prevention against column removal scenario is about twice of the accepted criteria that FEMA 350 has suggested for seismic loads.

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The aim of this article is to compare a direct hybrid system of gas turbine and solid oxide fuel cell with an indirect system from thermodynamic and exergy viewpoints. According to importance of fuel cell role in hybrid cycles and providing further proportion of produced power, discrete and complete thermodynamic, electrochemical and thermal analyses have been done. Calculation of working temperature which has an impact on system performance is one of the most significant works that is done in this article. In addition, by parametric study of this hybrid system, the influence of inlet air rate and compression ratio on efficiency, power and exergy destruction rate has been perused and eventually an optimized state for system will be offered. Results indicate that a direct hybrid system is more efficient in comparison with an indirect system. Higher efficiency, less irreversibility, higher power, and less pollution are the most important advantages of direct hybrid systems.

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Pseudo-static method is one of the oldest and simplest techniques for seismic stability analysis of embankment dams. Selection of appropriate seismic coefficients is the foremost part of analysis in Pseudo-static method. Previous researchers and design manuals often suggest constant values for selecting the seismic coefficient, regardless of geometry and stiffness of foundation and the dynamic characteristics of the structures. In the proposed method, the seismic coefficient is a function of parameters α and β. Parameter β is indicative of acceleration amplification in the direction of the dam height, and is related to the geometrical specifications and material properties of the dam body and foundation. Therefore, β can be obtained through dynamic analysis. In this research, in order to obtain the effect of foundation on this parameter, a geometrical model of the Masjed Soleiman Dam has been analyzed dynamically using seismographs of earthquakes that occurred in different sites. Dam consultants used this value for the MDE of the Masjed Soleiman Dam site. Parameter was obtained by assessing the way in which the maximum acceleration varied at different points on the height of the dam. Also, the effect of far and near field records of earthquake are evaluated. In this research, the safety factor in a wedge corresponding to the seismograph that causes the allowable displacement in that wedge is assumed to be equal to one. Thus, available seismographs were scaled to peak acceleration values and, using them, the wedge displacement values were calculated. The safety factor changes were then calculated using the seismograph that caused the allowable displacement in the wedge. These safety factors were assumed to be equal to one, and the dynamic safety factor for each wedge was determined by comparison of the results obtained from the original seismograph. After comparison of the dynamic and pseudo-static safety factors, the desired safety factor was determined. The distribution of the horizontal acceleration corresponding to the safety factor was compared with the linear distribution of horizontal acceleration proposed in this article and the values of β were determined. Finally, a new technique to estimate the pseudo-static seismic coefficient is presented. Different conditions for foundation are assumed and results of analyses are evaluated. Results of this research imply that geometry, stiffness and   analyses have been compared and based on the comparison of axial forces in the nails (as the most important factor of the stability), the equivalent horizontal acceleration coefficient for the model is proposed. The applied forces cause the reinforcement tension and the mobilized tension force can overcome the soil tension weakness. Thus, predicting mobilized forces in soldier pile nails during earthquake is very important. The effects of most important parameters such as wall height, nail arrangements and soil types through numerical modeling of the soldier piles under dynamic loading by using FLAC have been investigated.

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Ballasted track are of the most common species of railway in our country. The aim of this paper is study of three-dimensional models suitable for railway ballasted track and Dynamic analysis of those using numerical method Runge-Kutta 4th Order Method, after the dynamic analysis is performed and finally responses related to railway components be determined. To analyze the effect of passing under the railway train, a function of loading time on the railway line is applied and the effect of dynamic response under loading is evaluated. Previous researchers in the field activities of the railway system modeling and analysis of the dynamics on the two-dimensional models have been done. But this article is trying to consider the transverse nodes, on previous models and comes in three-dimensional dynamic analysis of the numerical method to be done. In other words, a new perspective in this article, consider nodes for transverse railroad modeling and numerical analysis of it. Brief description of the numerical methods mentioned along with the solving algorithm is mentioned in this article. In this research, simulation and modeling for rails, tie, connections and railway superstructure layers, is considered as elements of lump mass, spring and damper is used. Traditional methods used for the design of rail lines, based on static loading and quasi-dynamic analysis, the line components are analyzed, but in this article, according to the theories discussed in relation to rail component vibration, and study of dynamic load effects on track components into the issue to be more realistic. Responses obtained from dynamic analysis can be as input and issues designed to optimize rail components.

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One of the problems that influence on seismic behavior of structures and associate designing to itself is the grouping of structural element within analyzing and design of structures. Generally this grouping is due to facilitate of performing the structures. This paper investigates these grouping effects on behavior of concrete structures with RC bending frame systems andmoderate ductility scale. Study cases that is used for assessment of these grouping effect contains buildings with 4, 8 and 12 story RC structures. Each of these buildings designed one time without grouping and several times with grouping consideration about columns of structures in the height direction of buildings.Codes that are used for design purposes are Iranian Seismic code and RC structure design code. IDARC program V7.0 is utilized for estimation of damage indices, maximum story drifts or displacements and energy dissipated by building structural systems to comparing thenonlinear seismic behavior of column grouped and non-grouped structures. Damage indices calculated by this program is based on modified Park-Ang-Wen model and represented individually by elements, stories and a total damage index. The selected structures are analyzed with nonlinear dynamic analyzing method under Tabas earthquake record using several peak ground accelerations (0.35g, 0.50g, 0.75g and 0.90g) and pushover analysis with force-control and displacement-control methods. Maximum responses such as maximum displacements, damage indices(with grouping and non-grouping design method) were used to realization result of this designing method.Comparing the result of nonlinear analysis showed increasing of damage with increasing of PGA. This is due to a better distribution of forces in the elements of structures in case of non-grouped designed structures. Analytical results showed that the effect of grouping in PGA less than 0.5g is not sensible, but in larger PGA the grouped designed structures suffer more damages. The grouping of structural elements causes to concentration of energy in elements that their demand to capacity ratio (D_E/C_E) is greater than others.This causes that these elements embroil more damage and save other element from greater damage.One of the other results of this designing method (Grouping of element) is formation of soft stories in the structure. Also the reason of this behavior is due to lumping of hysteretic energy on these stories. This subject causes to generate soft and weak story in the structure and increase the overall damage indices.Furthermore result of pushover analysis showed that grouped element structures have a more stiffness and so in a weak earthquake (a low PGA) have a less or equal damage index in comparison to non-grouped element structures. As an overall result determined when D_E/C_E for all elements is close to each other distribution of damage is uniform and vice versa.

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In this paper the behavior of framee, the process of plastic hinge formation and energy absorption of frames with two spans and one floor with three types of slab including bubble deck slab, hollow core slab and reinforced slab under three earthquake accelerations have been analyzed and compared. The results show that bubble deck slab and hollow core slab as rigid as normal reinforced slab, although bubble deck slab has higher strength and stiffness compared to other slabs. Partnering slab in analysis make period of slab reduce more over bubble deck slab and hollow core to the comparison of reinforced slab, have more effect on period reduction. Ultimate displacement of frame with reinforced slab reach to failure mechanism is more than two mentioned case, however frame with bubble deck slab reach to failure mechanism under stronger earthquake acceleration and smaller displacement than reinforced slab. Comparison base shear of three discussed case shows that maximum base shear is in bubble deck slab and minimum base shear is in normal reinforced slab. Formation of plastic hinge in frame with bubble deck slab is similar with that in frame with hollow core slab with the difference that plastic hinge in former occurs later at the top end of the middle column and two ends of middle beams. In fact, formation of plastic hinges in this frame requires higher acceleration because of the higher amount of concrete and stiffness. In all samples, plastic hinge first occur in the frame and then yielding lines occur in the tensile region of the slabs. The failure mechanism of slab and steel frame occur at the same time in frame with hollow core slab and reinforced slab; however, this is not the case in the frame with bubble deck slab and even though with occurring of yielding lines, the slab does not fail. The stress distribution due to gravity loads is symmetric across all the slabs; however, the increase rate of stress is different. This difference is particularly notable in seismic behavior of slabs in a way that the formation of plastic hinge and yielding lines in hollow core slab, because of the holes, is totally different with that of in reinforced slab. In comparison with other slabs and due to the formation of plastic hinge, reinforced slab absorb lower energy. Columns, beams and connections play different role in energy dissipation. In all frame, the contribution of connections to dissipate energy is minor and this is because yielding does not occur in connections. Contrary to the frame with reinforced slabs, because of yielding in several places of columns, columns dissipate energy more than beams in the frames with hollow core slabs. It was concluded that hollow core slab and bubble deck slab have maximum and minimum contributions to the energy dissipation, respectively.

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At a Compressed Natural Gas (CNG) filling station, natural gas is stored in the high pressure reservoirs. The pressures within these reservoirs have huge effects on fast filling process of a natural gas vehicle’s (NGV) cylinder and the difficulties associated with the filling process. The accurate modeling of the fast-fill process is a complex procedure which should be thoroughly studied to optimize the filling process. Here, a theoretical analysis has been developed to study the effects of various parameters on the CNG filling process and the conditions. The analysis is based on the first and second laws of thermodynamics, conservation of mass and the AGA8 equation of state. The required properties of natural gas mixtures have been calculated making use of the AGA8 equation of state (EOS) and thermodynamics relationships. It is found that, the composition of natural gas is very effective on the CNG filling process and final in-cylinder values. For various Iranian natural gas compositions, the optimized filling stations' reservoirs pressure has been found.

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Abstract: Regard to investigations that are done about destructive earthquakes contemporarily and by contemplating on effects of different earthquakes on various types of structural systems and by recording acceleration of ground motions , researchers detected different effects of destruction in range about 15 to 60 kilometers far from epicenter of earthquake that is nominated as near fault earthquakes. the subsequences of researches which have been done in this field shows that mapping near to the fault have less effective time than mapping which are far from the fault and have one or more special pulse with a large domain and with medium to large frequency which causes to increase the domain of response spectrum in the zone of large period. and applying huge energy in short time and Sudden intense pulse in the beginning of near fault timehistories causes increasing the demand of rotational ductility in some stories and joints. In this article Regard to reliability of steel plate shear walls in recent four decades and also the fact that these structural systems have appropriate ductility to control displacements, height energy dissipation and ductile failure mechanism, the dynamic behavior of these systems is investigated .Four finite element models of 3,7,15 and 25 story buildings that used steel thin plate shear wall with hinge beam to column connections as resistant systems has created and analyzed through nonlinear dynamic analysis in ABAQUS finite element software and then response of structures such as story shear and drift angles of stories were detected. Results postulate the effects of shear distribution in near fault and regard to these purposes it seems that this fact is caused of effects of higher modes in far fault earthquakes. This situation cause of the fact that the frequency containers of near fault earthquakes are higher in range of height periods .besides Response of structures such as damage index and base shear, show that in tall steel plate shear walls (T>0.7s) effect of near fault movements on response parameters are more than those in the far fault zone. It also can be seen that base shear of the structures in far fault earthquakes fluctuates in more extended range compared to which happens in near fault structures and in near fault earthquakes base shear of most time histories don’t have much differences but in far fault earthquakes differences are relatively much. By increasing the height of SPSW’s differences between displacements in near fault and far fault earthquakes ascends. Maximum of differences between near fault and far fault responses appear in boundary of 40% to 60% of height of walls. Eventually can be said that not only higher PGA of most near fault earthquakes is a distinctive attribute in accordance with far fault earthquakes, but also higher frequency container in long period range would be devastating, regardless to higher PGA of these earthquakes.

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Currently, seismic design provisions of most building codes are based on strength or force (base shear) considerations. These building codes are generally regarding the seismic effects as equivalent static forces with a height wise distribution which is consistent with the first vibration mode shape. However, the design basis is being shifted from strength to deformation in modern performance-based design codes. This paper presents a practical method for optimization of steel moment resisting frames (SMRF), based on the concept of uniform deformation theory. This theory is based on this concept that the structural weight of a lateral load resisting system with uniformly distributed ductility demand-to-capacity ratio (or any other damage index) will be minimal compared to the weight of an ordinary designed system in which deformation is not distributed uniformly and just some of structural elements have reached their ultimate states. The state of uniform deformation can be achieved by gradually shifting inefficient material from strong parts of the structure to the weak areas. In the first part of this paper, the uniform deformation theory is implemented on 3, 5 and 10 story moment resisting frames subjected to 12 earthquake records representing the design spectrum of ASCE/SEI 7-10. This includes design of an initial structure according to conventional elastic design procedures, followed by an iterative assessment process using nonlinear dynamic analyses till the state of uniform deformation is achieved. Results show that the application of uniform deformation theory leads to a structure with a rather uniform inter-story drift distribution. Subsequently, the optimum strength-distribution patterns corresponding to these excitations are determined, and compared to four other loading patterns. Since the optimized frames have uniform distribution of deformation, they undergo less damage in comparison with code-based designed structures. Also, as the shear strength of each story is in proportion to the weight of that story, the optimized structures have minimum structural weight. For further investigation, the 10 story SMRF is redesigned using four existing load patterns and subjected to 12 earthquake excitations. Then a comparison is made between maximum beam rotations of each model and those belonging to the optimized one which revealed that the optimized SMRF behaves generally better than those designed by other loading patterns. Also, it is found that for none of the conventionally designed SMRFs, beam rotation demand is distributed uniformly. In other words, for all of the considered load patterns the maximum rotation of the beams in some stories exceeds the rotation associated with the performance level. Finally, assuming that the probability distribution of maximum rotations under different excitations follows a lognormal distribution, the probability of exceeding the allowable rotation associated with the LS performance level is calculated for different load patterns and compared to each other. Based on this comparison, the efficiency of each loading pattern is evaluated and the best one is determined. Application of optimization method presented in this paper avoids the concentration of deformation and damage in just one story and makes each story deformation and damage uniform over the height of the structure.

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In seismic performance based design procedures, nonlinear static pushover analysis (SPO) and incremental dynamic analysis (IDA) are usually used for determining seismic demand and capacity of moment resisting frames (SMR). The results of these methods are often presented using curves of intensity measures (IM) Vs damage indexes (DI). For far field earthquakes, different intensity measures, such as acceleration spectral intensity of the first mode of vibration with 5% damping i.e. Sa (T1, %5) factor are used. But for near field earthquakes, it is necessary to consider other suitable IM's. In this article, the difference between IDA and SPO curves for near field earthquakes compared to that for far field earthquakes are shown for three SMR frames which are designed according to Iranian code of practice using 15 pairs of near and far field earthquakes. Then some other intensity measure factors which may be suitable for near and far field earthquakes, are considered. These IM's are compared with the use of standard definitions of "efficiency" and "sufficiency". It is concluded that intensity measure IM1I&2E which considers second mode effects and nonlinear behavior, is much more efficient and better sufficient than more often used Sa(T1, %5) factor.

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Dams shall safely retain the reservoir and any stored solids, and pass environmentally acceptable flows, as required for all loading conditions, ranging from normal to extreme loads, commensurate with the consequences of failure. The new trend for performance-based design is to consider 2 levels of seismic actions and analyze the situation where the limit of force balance is exceeded for high intensity ground motions, associated with a very rare seismic event. For the design, two basic requirements are defined: (i) Non-collapse requirement (ultimate limit states), i.e. after the occurrence of the seismic event, the structure shall retain its structural integrity, with respect to both vertical and horizontal loads, and adequate residual resistance, although in some parts considerable damage may occur, (ii) Minimization of damage (serviceability limit state) , i.e. after seismic actions with high probability of occurrence, during the design life of the structure, some parts can undergo minor damage without the need of immediate repair. This study evaluates the behavior of a typical earth dam by nonlinear seismic analyses, in two performance levels, named “Base Performance Level” and “Desired Performance Level.” The level of seismic action and related acceptance level of damage are defined for each performance level. In “Base Performance Level,” with seismic levels of OBE (0.3g) and MDE (0.5g), the structure shall be serviceable and repairable and in “Desired Performance Level”, with seismic levels of MDE (0.5g) and MCE (0.7g), the structure shall be serviceable and repairable, respectively. Also, the stability of dam has been assessed by the “Strength Reduction Analysis.” The analyses are nonlinear and the constitutive law of the materials was assumed to follow "Finn" and "Mohr-Coulomb" models, incorporated into “FLAC 2D” finite difference analysis program. The factors such as initial shear modulus, variation of shear modulus versus shear strain, generation and dissipation of pore pressure and hysteretic damping are considered in this study. In addition, using the scaling method of applying maximum acceleration, the response of dam is investigated in different maximum accelerations. The results show that the dam needs to be changed in geometrical specifications or seismically improved in “Desired Performance Level”, in contrast with “Base Performance Level.” Results are confirmed by low amount of safety factors of stability in dam, which are calculated for different seismic loads. Also, the behavior of dam is examined by sensitivity analysis for type of accelerograms, constitutive model and the standard penetration number in shell of dam. Two accelerograms, including “Friulli” and “Sakaria” are considered. Maximum acceleration and duration of both of them are equalized and frequencies more than 5Hz are filtered. Sensitivity analyses of “Friulli” and “Sakaria” accelerograms, despite the difference in response spectra and specific energy density, show approximately similar results. “Finn” model predicts the amount of excess pore water pressure to be more than "Mohr- Coulomb" up to %20, and shows the occurring of liquefaction in SPT more than 35 and acceleration more than 0.7g, in shell of upstream of dam

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Concrete buttress dams are constructed in large numbers at medium sites in many countries such as Iran because of their considerable technical and economical benefits in previous century. This type of dams is exposed to damages due to earthquakes as other structures. Some buttress dams such as Sefidroud dam in Iran, Hsinfengkiang dam in China and Honenike dam in Japan have undergone some damages due to recent earthquakes. After these incidents, some investigations have been carried out. However, these investigations have just mentioned the manner of incidents and the resulting damages. Therefore, the seismic behavior and sensitivity recognition of these dams with respect to different factors have been ignored; however the study of behavior and seismic sensitivity of this type of dams is important. In this paper, the tallest monolith of the Sefidroud concrete buttress dam is analyzed using a 3D model with massless foundation to study the seismic behavior and sensitivity of this type of dam. The interaction of the dam with the reservoir, the reservoir bottom absorption and upstream radiation of hydrodynamic waves are considered, but the cross-canyon component of earthquake is neglected. The applied accelerograms to the system are scaled according to the Sefidroud dam site DBE response spectrum. To determine the initial conditions before occurring earthquake, a series of detailed static analyses are done under the effect of dam body weight, hydrostatic pressure, uplift pressure and ambient temperature. Seismic loading due to longitudinal and vertical components of earthquake is applied and the nonlinear behavior of dam under various factors such as different seismic loading scenarios and different properties of dam body and also foundation materials is investigated. The results of analyses show that the dam body downstream kink, heel, toe and buttress web are sensitive and vulnerable zones. The results also demonstrate that the compressive stresses in the dam body are usually much less than the compressive strength of concrete. Therefore, the possibility of compressive failure is almost zero. But the conditions of tensile and shear stresses are different and large stresses may occur at the mentioned zones and considerable tensile and shear damages to the dam body are possible. According to the results of analyses, it is apparent that when the ratio of dam body modulus to that of the foundation (called softness modulus) is small, i.e. when the foundation modulus is high and near to that of dam body, the construction of concrete buttress dams at highly seismic zones may cause local failure and unfavorable situations for the tensile stresses at the kink, the heel and the toe of the dam body. Therefore, adaptation of this dam type in such sites should be carefully studied and in these circumstances, the modulus of the concrete of dam body should be kept more than usual practice. Furthermore, the shear damage at the dam-foundation contact surface is highly dependent to the applied earthquake type, but increasing the softness modulus could reduce this type of damage. The compressive strength of concrete has no effect on the shear damage at the dam-foundation contact surface.

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Structural redundancy is a non-independent concept in structural engineering and has inherent dependence on structural parameters such as overstrength and ductility, so that both of overstrength and ductility capacities should change corresponding to any variation in structural redundancy. Nevertheless, most of researchers notified that taking any increase in structural redundancy should be a desirable property to deal with more effectively against earthquake loading. Furthermore, this issue can reduce structural sensitivity to abnormal loads. In this research to clarify the pure role of redundancy in earthquake resistant design and to distinguish the role of redundancy from total overstrength capacity, a number of 3D reinforced concrete special moment resistant frames (RC-SMRF) with equal ultimate base shear coefficient were designed. The dynamic behavior parameters of the designed structures under natural strong ground motion were evaluated, especially with regards to configuration of nonlinear deformations. The analytical outputs obtained from analyzed structures are illustrated ensembles of maximum acceleration, maximum velocity and maximum drift of each story. Furthermore, adequacy and accuracy of response modification factor which should be assigned as general indicator of quality of total seismic behavior has been studied conceptually. The results of this research indicate that: (i) Assigning an increase in structural redundancy would not always lead to efficient improvement in structural seismic behavior. Furthermore, notification to process of increased redundancy should not be consider as a criterion for any basic improvement in structural performance. This issue means that it is better to consider the effects of redundancy on important seismic parameters such as both the structural member ductility and the overstrength capacity. (ii) The calculated response modification factors as mentioned in this research, can consider as an index of quality of structural dynamic performance which is corresponding to a certain level of redundancy. Accordingly, the above statement should be notified in general cases of those earthquake loadings which would cause a certain level of story drift. This certain level of story drift would denote the structural behavior typically follows the calculated response modification factor. Oppositely, if an earthquake loading causes more story drift from that assigned certain level, structural behavior typically does not follow the calculated response modification factor. (iii) The codified procedure of calculation of response modification factor which were discussed and assessed in this study, cannot be realized subjected to those input strong ground motions that able to display high amplitude and long period pulse or pulses in their velocity time history. It is important to know that strong near-fault ground motions often have an impulsive feature and impose large amounts of sudden intense kinematic energy which must be dissipated by structural system during a short period of time. This issue causes amplified deformation demands in structures which are associated with very few cycles of cumulative plastic deformations. Hence, the earthquake damages due to these seismic load cases are effectively related to maximum deformation as well as maximum ductility. Yet, structures cannot accomplish based on the calculated response modification factor in the mentioned cases.